U.S. patent application number 12/270603 was filed with the patent office on 2009-06-11 for tensioner anti-rotation device.
Invention is credited to Fife B. Ellis, Joseph W. Pallini, JR..
Application Number | 20090145611 12/270603 |
Document ID | / |
Family ID | 40639449 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090145611 |
Kind Code |
A1 |
Pallini, JR.; Joseph W. ; et
al. |
June 11, 2009 |
TENSIONER ANTI-ROTATION DEVICE
Abstract
A tensioner anti-rotation device and method that transfers
rotational force from an offshore platform deck to a riser in
response to waves and currents. The device includes a bracket
mounted on the deck, and a rib that transfers force from the deck
through the bracket, to the rib, and into the riser such that the
tensioners on the riser are not subjected to torque.
Inventors: |
Pallini, JR.; Joseph W.;
(Tomball, TX) ; Ellis; Fife B.; (Houston,
TX) |
Correspondence
Address: |
Patent Department
GE Oil & Gas, 4424 West Sam Houston Parkway North
Houston
TX
77041
US
|
Family ID: |
40639449 |
Appl. No.: |
12/270603 |
Filed: |
November 13, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60988188 |
Nov 15, 2007 |
|
|
|
Current U.S.
Class: |
166/355 ;
405/224.4 |
Current CPC
Class: |
E21B 19/004
20130101 |
Class at
Publication: |
166/355 ;
405/224.4 |
International
Class: |
E21B 19/09 20060101
E21B019/09; E21B 19/086 20060101 E21B019/086; E21B 15/02 20060101
E21B015/02 |
Claims
1. A tensioner anti-rotation device for transferring rotational
force from deck of a floating platform to a riser, the tensioner
anti-rotation device comprising: a first member adapted to be
secured to the riser; and a second member adapted to be secured to
the floating platform, wherein the second member blocks rotational
movement of the first member relative to the second member and
enables movement of the first member relative to the second member
along an axis of the riser.
2. The anti-rotation device of claim 1, wherein one of the first
member or the second member comprises a key and one of the second
member or the first member comprises a slot adapted for vertical
sliding engagement with the key.
3. The anti-rotation device of claim 1, wherein the key is adapted
to be mounted to the riser and slot is adapted to be mounted to the
deck.
4. The anti-rotation device of claim 1, wherein the key comprises a
rib adapted to be mounted to riser, and the rib has a greater
longitudinal length than the slot.
5. The anti-rotation device of claim 1, wherein the slot is formed
in a bracket adapted to be mounted to the deck.
6. The anti-rotation device of claim 1, wherein the slot is adapted
to be located on the riser and has a greater longitudinal length
than the key.
7. The anti-rotation device of claim 1, wherein a guide roller is
adapted to engage the riser, the slot is located in the guide
roller, and the key is adapted to be mounted to riser.
8. The anti-rotation device of claim 1, wherein the key comprises a
protuberance on a bracket adapted to be mounted to the deck.
9. In an offshore well installation having a riser extending upward
from a subsea well, a floating platform having an opening through
which the riser extends, a riser tensioner mounted to the platform
at the opening for applying tension to the riser, and a set of
guide rollers mounted to the platform at the opening and in
engagement with the riser, the improvement comprising: a key and
slot arrangement mounted between the riser and the platform for
inhibiting rotation of the platform relative to the riser.
10. The anti-rotation device of claim 8, wherein the key is mounted
to the riser and the slot is mounted to the deck.
11. The anti-rotation device of claim 8, wherein the key comprises
a rib mounted to the riser, the rib has a greater longitudinal
length than the slot.
12. The anti-rotation device of claim 8, wherein the slot is formed
in a bracket mounted to the deck.
13. The anti-rotation device of claim 8, wherein the slot is
located on the riser and has a greater longitudinal length than the
key.
14. The anti-rotation device of claim 8, wherein a guide roller
engages the riser, the slot is located in the guide roller, and the
key is mounted to riser.
15. The anti-rotation device of claim 8, wherein the key comprises
a protuberance on a bracket mounted to deck.
16. The anti-rotation device of claim 8, wherein the riser further
comprises: a cylindrical sleeve rigidly attached to and surrounding
an inner cylinder of the riser; a flange at upper end of sleeve; a
flange at lower end of sleeve; and wherein the key is mounted to
the sleeve and the slot is mounted to the deck.
17. A method for applying tension to a riser, the method
comprising: securing a first end of a tensioner cylinder assembly
to a riser and a second end of the tensioner cylinder assembly to a
floating platform to enable the tensioner cylinder assemblies to
place the riser in axial tension; and coupling the riser to the
floating platform to prevent rotational movement of the first end
of the tensioner cylinder assembly relative to the second end of
the tensioner cylinder assembly.
18. The method of claim 17, wherein coupling the riser to the
floating platform comprises securing a key to the riser and
securing a slot to the deck, the key and slot being configured for
vertical sliding engagement.
19. The method of claim 16, wherein coupling the riser to the
floating platform comprises securing a key to the deck and securing
a slot to the riser, the key and the slot being configured for
vertical sliding engagement.
20. A tensioner assembly for applying tension to a riser,
comprising: a first member securable to the riser; a plurality of
cylinder assemblies coupleable between the first member and a
platform, wherein the plurality of cylinder assemblies are adapted
to apply a tensile force to the riser via the platform and the
first member; and an anti-rotation assembly adapted to restrict
rotational motion of the riser relative to the platform to prevent
twisting of the plurality of cylinder assemblies due to rotational
motion of the platform.
21. The tensioner assembly of claim 20, wherein the anti-rotation
assembly comprises: a key adapted to be coupled to one of the riser
or the platform; and a slot adapted to be coupled to one of the
riser or the platform in vertical sliding engagement with the slot.
Description
[0001] This application claims priority from the provisional
application Ser. No. 60/988,188. filed Nov. 15, 2007 entitled
"Tensioner Anti-Rotation Device," which is incorporated by
reference herein in its entirety.
BACKGROUND
[0002] 1. Field of Invention This invention relates in general to
devices for tensioning risers for offshore well production, and in
particular to a device that causes the upper portion of the riser
to rotate along with the vessel if the vessel rotates due to waves
and currents.
[0003] 2. Description of Related Art
[0004] Offshore production platforms must support production risers
from oil or gas wells which extend to the platform from subsea
wells. For platforms that are fixed to the ocean floor this is
readily accomplished and is well known in the art. However, for
subsea completions in deep water that require the use of floating
platforms, such as tension leg platforms or semi-submersible
platforms, supporting risers present significant problems. These
platforms move under the influence of waves, wind, and current and
are subjected to various forces, including rotational forces. Thus,
the riser tensioning mechanism must permit the platform to move
relative to the riser and care must be taken that the tensioning
mechanism can withstand rotational forces.
[0005] The riser tensioning mechanism must also maintain the riser
in tension so that the entire weight of the riser is not
transferred to the wellhead and so that the riser does not collapse
under its own weight. The tensioning mechanism must therefore exert
a continuous tensional force on the riser. Also, this force must be
maintained within a narrow tolerance. The use of a hydraulic
cylinders attached between a platform and a riser to support the
weight of the riser is well known in the art. The tensioner
cylinders of the prior art are exposed to torque resulting from
vessel rotation in response to environmental forces such as waves,
currents, and wind. Improvements to protect the tensioner cylinder
from this torque are desired.
SUMMARY OF INVENTION
[0006] The present invention disclosure comprises a tensioner
anti-rotation device and method for transferring rotational force
from the deck of a floating platform to a riser, thereby protecting
tensioner cylinders from torque produced by vessel rotation in
response to environmental forces such as waves, currents, and
wind.
[0007] The apparatus comprises a key adapted to be mounted either
to the riser or the deck; with a slot adapted to be located on the
other of the riser or the deck, in vertical sliding engagement with
the slot. The apparatus preferably includes two brackets mounted on
the vessel's deck. Each bracket can have either a key or a slot on
its inner side and is preferably located 180.degree. apart from the
other. Each bracket is in proximity to the riser and tensioner
cylinders. An axially extending key or slot is located on the
riser, or on an attached sleeve. The key and slot arrangement
between the riser and deck-mounted bracket loosely engage, allowing
axial movement of the arrangement with respect to the riser. The
system allows for axial movement that is greater than the stroke
length of the tensioner cylinders.
[0008] Where the key comprises a rib adapted to be mounted to the
riser, the rib has a greater longitudinal length than slot.
However, if the slot is adapted to be located on the riser, the
slot then has a greater longitudinal length than the key.
[0009] When the vessel rotates, the key and slot arrangement on the
riser and bracket engage, with the key contacting the inner portion
of the slot. The contact between the key and slot transfers the
torque from the deck, the bracket, through the key and slot
arrangement, and to the riser. The tensioner cylinders are thus
protected from torque that could disturb their alignment or result
in damage.
[0010] The apparatus could also include a guide roller adapted to
engage riser in lieu of brackets. The guide roller is mounted to
the deck and has a slot, with a key adapted to be mounted to the
riser.
BRIEF DESCRIPTION OF DRAWINGS
[0011] Some of the features and benefits of the present invention
having been stated, others will become apparent as the description
proceeds when taken in conjunction with the accompanying drawings,
in which:
[0012] FIG. 1 is a perspective view illustrating a riser tensioner
constructed in accordance with this invention
[0013] FIG. 2 is a side elevational view of the riser tensioner of
FIG. 1.
[0014] FIG. 3 is a sectional view of a portion of the riser of FIG.
2, illustrating the attachment of a sleeve.
[0015] FIG. 4 is a sectional view of the riser tensioner of FIG. 2,
taken along the line 4-4 of FIG. 2.
[0016] FIG. 5 is a side elevational view of an alternate embodiment
of the riser tensioner constructed in accordance with this
invention.
[0017] FIG. 6 is a sectional view of the riser tensioner of FIG. 5,
taken along the line 6-6 of FIG. 5.
[0018] FIG. 7 is a side elevational view of another embodiment of a
riser tensioner constructed in accordance with this invention.
[0019] FIG. 8 is a sectional view of the riser tensioner of FIG. 7,
taken along the line 8-8 of FIG. 7.
[0020] FIG. 9 is a side elevational view of still another alternate
embodiment of a riser tensioner in accordance with this
invention.
[0021] FIG. 10 is a sectional view of the riser tensioner of FIG.
9, taken along the line 10-10 of FIG. 9.
DETAILED DESCRIPTION OF INVENTION
[0022] Referring to FIG. 1, riser tensioner assembly 11 provides
tension to a riser 13 that has its lower end secured to subsea
equipment such as a subsea wellhead assembly (not shown). Riser 13
extends upward through an opening 15 in a deck 17 of the vessel.
Although moored, typically the vessel will move relative to riser
13 in response to current and wave motion. A plurality of cylinder
assemblies 19 are supplied with hydraulic fluid and gas under
pressure to provide an upward force to riser 13 to maintain a
uniform tension in riser 13 as deck 17 moves relative to riser 13.
Cylinder assemblies 19 are conventional, each having a piston and
piston rod. A lower end of each cylinder assembly 19 is mounted to
deck 17 and an upper end is mounted to a clamp assembly 21, which
clamps to riser 13. A plurality of guide rollers 23 may be employed
to centralize riser 13. Guide rollers 23 are mounted
circumferentially around riser 13 for rolling engagement with riser
13, or a component mounted to riser 13.
[0023] In this embodiment, a cylindrical sleeve 25 is mounted
around riser 13. Sleeve 25 is rigidly attached to and surrounds an
inner cylinder of the riser 13 so that it will not move axially or
rotationally relative to riser 13 and thus may be considered as
part of the riser 13. Sleeve 25 has a length greater than the
maximum stroke of cylinder assemblies 19 from the contracted to the
extended positions so that rollers 23 remain in engagement with
sleeve 25.
[0024] In this example, sleeve 25 has an inner diameter larger than
an outer diameter of riser 13, defining an annular clearance
between them. Sleeve has a flange 27 at its upper and lower ends
that extends radially outward. An axially extending key or rib 29
is mounted on the exterior of sleeve 25 and extends from the lower
flange 27 (FIG. 2) to the upper flange 27. Rib 29 may be attached
either by welding or fasteners. Rib 29 may have a rectangular or
other configuration in cross-section.
[0025] Sleeve 25 may be secured to riser 13 in a variety of manners
so as to be rigidly attached. In this embodiment, as shown in FIG.
3, flange 27 has a tapered inner diameter 31. A split bushing 33
has a tapered surface 35 that faces outward and mates with tapered
surface 31. Split bushing 33 is placed around riser 13 then clamped
tightly to flange 27, such as by fasteners. Split bushing 33 has an
inner diameter slightly smaller than the outer diameter of riser 13
so that when secured to flange 27, it wedges sleeve 25 into tight
engagement with riser 13. A similar arrangement for securing sleeve
25 will be located on the lower flange 27.
[0026] Referring to FIG. 4, a bracket 37 is mounted to deck 17
(shown schematically) for each rib 29. In the embodiment of FIG. 4,
there are two keys or ribs 29, each located 180.degree. apart from
the other; however, fewer or more ribs 29 could be employed. Each
bracket 37 has a slot 39 on its inner side that fits loosely around
three sides of one of the ribs 29. As deck 17 moves upward and
downward relative to riser 13, brackets 37 will slide up and down
ribs 29. If a rotational force occurs, such as from current or
yawing of the vessel, this rotational force is transferred from
deck 17 through brackets 37, ribs 29, sleeve 25 and to riser 13.
The upper portion of riser 13 will rotate with the vessel. The
engagement between brackets 37 and ribs 29 causes the upper portion
of riser 13 to twist or rotate in unison with deck 17. This
arrangement avoids a twisting force or torque being transferred
through cylinder assemblies 19.
[0027] Other devices may be employed to cause riser 13 to twist if
the vessel rotates. For example, the embodiment in FIGS. 5 and 6
does not employ a sleeve 25. Rather, key or rib 41 is attached
directly to riser 13, such as by cap screws 43. As shown in FIG. 6,
brackets 45 may be identical to brackets 37 of FIG. 4. Brackets 45
have slots that receive ribs 41.
[0028] In FIG. 7, rather than a key or rib, a slot 47 is formed,
and in this example, slot 47 is formed directly in riser 13,
although it could be formed within a sleeve. Slot 47 extends
axially along riser 13 in the same manner as ribs 41 (FIG. 5) and
ribs 29 (FIG. 2). As shown in FIG. 8, brackets 49 are mounted to
deck 17. Each bracket 49 has a key or tongue 51 that locates within
one of the slots 47. Tongue 51 is able to slide up and down within
slot 47, and will transmit any rotational force from deck 17 to
riser 13. Rollers 23 engage riser 13. Alternatively, one or more
rollers having a central rib that is inserted into slot 47 may be
used.
[0029] Referring to FIG. 9, in this embodiment, a sleeve 53 is
rigidly attached to riser 13. Sleeve 53 may be attached by flanges
55 and a split bushing (not shown) in the same manner as sleeve 25
of FIG. 2. Keys or ribs 57 are secured to the outer diameter of
sleeve 53, either by welding or fasteners. As shown in FIG. 10, in
this embodiment, there are two ribs 57, each spaced 180.degree.
apart. Rather than a separate bracket, such as bracket 37 (FIG. 4)
or bracket 45 (FIG. 6), each rib 57 is engaged by a central portion
61 of one of the rollers 59. In this example, two of the rollers 59
have one of the central portions 61, each central portion 61 being
of smaller diameter than the outer end portions. The outer end
portions engage the outer diameter of sleeve 53. Each central
portion 61 engages one of the ribs 57 to transfer any torque
imposed by rotational movement of the vessel through rollers 59
into riser 13.
[0030] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. These embodiments are not intended to limit the scope of
the invention. The patentable scope of the invention is defined by
the claims, and may include other examples that occur to those
skilled in the art. Such other examples are intended to be within
the scope of the claims if they have structural elements that do
not differ from the literal language of the claims, or if they
include equivalent structural elements with insubstantial
differences from the literal language of the claims.
* * * * *